Mentor Graphics has two primary tools that you (a 6.195 student) will be interested in using. These are Design Architect and QuickSimII. Design Architect is the tool that is used to input a schematic. Components can be from the standard library functions compiled or can be created from VHDL source code. Once a schematic is successfully entered, QuickSimII is used to check the schematic via simulation.

2. Booting Design Architect

Mentor Graphics only runs on the Hp machines in the lab. To start up Mentor's Design Architect tool, first set up your dot files:

athena% source /fs/u27d/mentor.cshrc

It is better to create a separate directory for your schematic BEFORE entering design architect. To create a directory, use the mkdir command. Now use cd to change into that directory. Then start the program:

athena% da >&/dev/null &

You should see the design architect window pop up. Notice that on the right side of the screen there is a reddish bar that looks like a brick wall; this is your drawing palette. To expose the palette, the screen needs to be enlarged. Drag the window to the lower left corner of the screen, and pull the top bar to expand the window to the size of the screen. The session_palette will now be visible.

Design Architect stores the different layers of a cicruit schematic on "sheets." To open a sheet, click on the "Open Sheet" icon on the palette. Type in the component name being drawn on the sheet, and click OK. Note that Mentor IS case sensitive. You should now see a black window with dots appear within the original window. Notice also how the session_palette has been replaced with the schematic palette. You are now ready to begin drawing.

During the course of drawing, should you ever decide to quit the program, the correct way of exiting is by typing Shift-F12 . There is no exit command that can be found through any one of the menus.

3. A Simple Example

This example was chosen to illustrate two aspects of designing with Design Architect. The first is to show how to create components from the standard libraries provided (such as the LS74 series library). The second is to show how a box described in VHDL can be inserted in the schematic.

The circuit designed really has no useful function, except that it is simple. It consists of a 74LS163 counter and a VHDL entity. The VHDL entity takes as input the four outputs of the counter, and sets its output high whenever exactly two of the counter outputs are high. The vhdl code is shown below.

library ieee;
use ieee.std_logic_1164.all;

entity blackbox is port (
a,b,c,d: in std_logic;
result: out std_logic);
end blackbox;

architecture combinational of blackbox is
begin
result <= (a and b) or (a and c) or (a and d) or (b and c) or (b and d) or (c and d);
end combinational;

4. Entering the Schematic

Step 1: Place the 74LS163
Since the counter is a standard library component, click on the Library icon from the palatte. Select ls_lib from the menu. Scroll down by clicking once next to the last item in the menu until you find the 74LS163a. Double click on this selection. If you then drag your mouse over the black drawing window, you will see the parts icon appear. Click once somewhere in this screen to place the part. You can zoom in or out by going the the lower left corner of the session screen, clicking on the right mouse button, and selecting which option you'd like from the menu. Zoom in or out as necessary so you can comfortably see the entire icon. You can retrieve the schematic palette by clicking with the right mouse button anywhere over the library menu and selecting Display Schematic Palette .

Step 2: Add the Portin Signals
Any input that is an input for the overall system needs to be connect to the portin symbol. For this system, the only input we'll have is a clock signal. Go back to ls_lib . This time select portin from the menu. Place the symbol next to the clock input of the counter, and click once. Use the Add Wire icon from the palette to connect the port to the clock pin.

Step 3: Connect the Rest of the Pins
Using the Add Wire icon, and the ground and vcc components in the ls_lib menu, connect the data inputs to ground, the ENP and ENT inputs to power, the LOAD pin to the RCO, and the CLR pin to power.

5. Simulation Using QuickSimII

Starting Up QuickSimII.
To start up QuickSim, type the following command at the athena prompt:

athena% quicksim.>&/dev/null &

Do not forget to type the period as shown in the command: that is correct! Also be careful to not leave any spaces between the characters in the command. 6. Solutions to Some Wacky Problems

Losing your session palette. The first time I ran Mentor, I did not know that by simply enlarging the screen, the session palette is reveled. In the process of trying to enlarge it, I accidentally lost the palette by clicking on "Hide Palette." (I know, very stupid, don't ask me why I did this!) Once the palette is hidden, however, I know of no way of actually getting it back, aside from saving your work, and rebooting Design Architect all over again. Message: Don't ever hide your palettes!
Erasing Text. Mentor does not understand either the backspace or del keys as delete; rather, the text you wish to erase or retype must be highlighted first, and then delete or the new letter typed to erase it.

Dangling pins. Make sure they're properly connected. Note that all pins must be defined as connected to something. Purposeful dangles should be declared as a "not connected" pin.

7. Useful Design Architect Commands

F1: Selects whatever object the mouse is over.
F2: Deselects everything.
Shift-F12: Exits any Mentor application. Note that you will need to first exit the sheet, before you can exit Design Architect or QuickSimII completely.

8. Links to Other Useful Sites

Mentor Graphics Tool Suite for 6.111
Design Architect Main Page
QuickSimII Main Page